The present invention relates to a spectrophotometer system and, more particularly, a base-line correction means for a spectrophotometer system controlled by a computer.
In a spectrophotometer system for measuring optical data such as transmission or apparent reflectance of visible light as a function of wavelength, conventionally, several discrete values of independent variables are sampled for recording or data processing in the spectrophotometer system controlled by a computer.
A base-line as used herein means a line drawn in a graphical representation of a varying physical quantity such as a voltage to indicate a reference value such as the voltage value which is measured in the absence of any samples. A base-line correction as used herein means to calculate true values when any sample is applied by subtracting the reference value from measured values.
To cause the base-line correction, it is ideal that several discrete values used for the base-line correction are measured and memorized in the computer. However, this requires a great capacity of a computer memory so that it is impractical.
Therefore, the several discrete values for the base-line correction are thinly measured more than the sampled and measured values. The several discrete values are memorized in the computer memory. The values for the base-line correction are calculated with interpolation, the values being applied to the measured values in the sampling points except for the base-line correction sampling points.
However, for this interpolation, the values for the base-line correction must be calculated at every one of the sampling points, so that such calculation needs a long time and, therefore, scanning speed for measurement must be limited to slow speeds.
In view of these problems, it is desired to minimize the time used for calculating the values for the base-line correction with a small computer memory.